Questions about Java interface and abstract

Question1

Which of the following statements tests for CONTENT equality?

if ( x == "Hello" ) { ... }

if ( x.equals( "Hello" ) ) { ... }

if ( x != "Hello" ) { ... }

if ( x.contains( "Hello" ) ) { ... }

None of the above

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Question 2

Which comparison below is acceptable in Java syntax if the following declarations are made? CSC142Point p1 = new CSC142Point( 3, 4 ); CSC142Point p2 = new CSC142Point( 5, 6 );

p1.getX() > p2.getX()

p1.setX(5) == p2.setX(5)

p1 < p2

all of the above

none of the first 3 are acceptable syntax in Java

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Question 3

Which of the following statements creates a composition (or aggregation) relationship?

public doSomething(Boo b){ ...}

return new Boo();

if ( myThing == b ) { ... }

private Boo myThing;

Boo Hoo

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Question 4

Which of the following things may an abstract class contain in addition to abstract methods?

method definitions with implementations

instance variable declarations

constructor definitions with implementations

class constants (final variables)

All of the above.

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Question 5

What is the difference between an abstract class and a concrete class?

An abstract class may NOT be extended.

An abstract class may NOT be instantiated.

All methods in an abstract class must be abstract.

A reference variable cannot have an abstract class as its static type.

All of the above.